The Associated Press reports that a Simi Valley, Calif., man took AT&T to court over its policy of throttling grandfathered, unlimited wireless data users when they become 5 percent of the heaviest users in a market. Today, a judge ruled against Ma Bell 2.0 in small claims court, awarding Matt Spaccarelli $850.

That amount isn’t much, of course, but it opens the door to a flood of similar cases that would have to be tried one-by-one, all because of a previous ruling in AT&T’s favor by the U.S. Supreme Court. More about that in a moment.

The judge ruled that AT&T essentially was being unfair in its throttling practice, according to the AP:

Pro-tem Judge Russell Nadel found in favor of Spaccarelli in Ventura Superior Court in Simi Valley on Friday, saying it wasn’t fair for the company to purposely slow down his iPhone, when it had sold him an “unlimited data” plan.

During today’s court session, an AT&T sales manager argued that the telco has the right to use throttling to keep its network from being congested. However, Spaccarelli said his throttling began between 1.5-2 gigabytes of usage, which is below the amount of data used by many customers who pay for tiered plans. The sales manager wouldn’t comment to the AP beyond what he said in court.

AP reporters Peter Svensson and Greg Risling note that AT&T has about 17 million customers still using its unlimited plan. Normally, a group like this could sue AT&T in a class action, but the carriers’ contract forbids such litigation – a provision that the U.S. Supreme Court ruled in 2011 was binding. The clause also forbids jury trials, limiting aggrieved customers to binding arbitration or small claims courts.

So what would happen if all of AT&T’s unlimited data customers who found themselves throttled took the company to small claims court? That would essentially keep the telco’s attorneys very, very busy.

You might even say its legal department would be . . . throttled.

An AT&T spokesman said the company hasn’t yet decided to appeal.

One other thing to note about this case: Spaccarelli had been illegally tethering his computer to his iPhone’s data connection.

Spaccarelli didn’t quite uphold his side of the customer contract, and that’s one reason his data usage was high. He used the iPhone to provide a link to the Internet for his iPad tablet, a setup known as “tethering.” AT&T doesn’t allow tethering unless customers pay extra for it, which Spaccarelli didn’t do. It detected his tethering last year, and switched him from the “unlimited” plan to a limited one. He complained, and got his “unlimited” plan reinstated.

Even with the tethering, Spaccarelli’s data usage wasn’t excessive, he said — about 5 gigabytes per month. AT&T’s [Peter] Hartlove told Nadel about the tethering, and Spaccarelli admitted to it.

Still, most of the people who find themselves throttled after using just a couple of gigabytes of data aren’t engaged in illegal tethering. They’re just using their smartphones as they always have, and being unfairly punished by AT&T for doing so.